Retransmission of data to or from a mobile station, MS, or user equipment, UE, is previously known. It is also known to use medium access control and radio link control layers of a UMTS protocol structure in acknowledged mode for dedicated channels.
In acknowledged mode, retransmissions are undertaken in case of detected transmission errors not recovered by forward error control. This is also called automatic repeat request, ARQ. With ARQ, retransmissions can be undertaken unless a transmitted message is (positively) acknowledged. Retransmissions could also be initiated at explicit negative acknowledgments of transmitted messages. Generally there are time limits for the respective positive and negative acknowledgements to be considered.
Within this patent application, a radio network controller, RNC, is understood as a network element including a radio resource controller. Node B is a logical node responsible for radio transmission/reception in one or more cells to/from a User Equipment. A base station, BS, is a physical entity representing Node B.
Medium access control, MAC, and radio link control, RLC, is used within radio communications systems like General Packet Radio Services, GPRS, and UMTS.
U.S. Pat. No. 5,570,367 discloses a wireless communications system arranged to transmit acknowledgement and request for retransmission messages. Data received in a microcell from an end user device is forwarded to a cell site. Data received by the cell site is transmitted to a cellular switch. A base station sends a poll message to the end user device, inquiring for the status of unacknowledged messages previously transmitted from the base station.
Also, a base station transmitter window is defined. A lower end pointer identifies a lowest numbered packet transmitted to and acknowledged by the base station. The upper end pointer identifies the highest numbered packet transmitted by the base station. Consequently, the window represents packets transmitted by the base station and unacknowledged by the end user device.
International Patent Application WO02096044 reveals a method and system of reducing or eliminating transmissions over a scarce communication link resource in a communications system by establishing an image of downlink transmissions status.
International Patent Application PCT/SE02/02186 includes a method and system for in-sequence delivery of RLC PDUs, transmitted in downlink direction, to a user equipment at handover.
3rd Generation Partnership Project (3GPP): Technical Specification Group Radio Access Network, Physical Layer Procedures, 3G TS 25.301 v3.6.0, France, September 2000, specifies in chapter 5 Radio Interface Protocol Architecture of a UMTS system. There are three protocol layers:                physical layer, layer 1 or L1,        data link layer, layer 2 or L2, and        network layer, layer 3 or L3.        
Layer 2, L2, and layer 3, L3 are divided into Control and User Planes. Layer 2 consists of two sub-layers, RLC and MAC, for the Control Plane and four sub-layers, BMC, PDCP, RLC and MAC, for the User Plane. The acronyms BMC, PDCP, RLC and MAC denote Broadcast/Multicast Control, Packet Data Convergence Protocol, Radio Link Control and Medium Access Control respectively.
FIG. 1 illustrates a simplified UMTS layers 1 and 2 protocol structure for a Uu Stratum, UuS, or Radio Stratum, between a user equipment UE and a Universal Terrestrial Radio Access Network, UTRAN.
Radio Access Bearers, RABs, make available radio resources (and services) to user applications. For each mobile station there may be one or several RABs. Data flows (in the form of segments) from the RABs are passed to respective Radio Link Control, RLC, entities which amongst other tasks buffer the received data segments. There is one RLC entity for each RAB. In the RLC layer, RABs are mapped onto respective logical channels. A Medium Access Control, MAC, entity receives data transmitted in the logical channels and further maps logical channels onto a set of transport channels. In accordance with subsection 5.3.1.2 of the 3GPP technical specification MAC should support service multiplexing e.g. for RLC services to be mapped on the same transport channel. In this case identification of multiplexing is contained in the MAC protocol control information.
Transport channels are finally mapped to a single physical channel which has a total bandwidth allocated to it by the network. In frequency division duplex mode, a physical channel is defined by code, frequency and, in the uplink, relative phase (I/Q). In time division duplex mode a physical channel is defined by code, frequency, and timeslot. The DSCH (Downlink Shared Channel), e.g., is mapped onto one or several physical channels such that a specified part of the downlink resources is employed. As further described in subsection 5.2.2 of the 3GPP technical specification the L1 layer is responsible for error detection on transport channels and indication to higher layer, FEC encoding/decoding and interleaving/deinterleaving of transport channels.
PDCP provides mapping between Network PDUs (Protocol Data Units) of a network protocol, e.g. the Internet protocol, to an RLC entity. PDCP compresses and decompresses redundant Network PDU control information (header compression and decompression).
For transmissions on point-to-multipoint logical channels, BMC stores at UTRAN-side Broadcast Messages received from an RNC, calculates the required transmission rate and requests for the appropriate channel resources. It receives scheduling information from the RNC, and generates schedule messages. For transmission the messages are mapped on a point-to-multipoint logical channel. At the UE side, BMC evaluates the schedule messages and deliver Broadcast Messages to upper layer in the UE.
3G TS 25.301 also describes protocol termination, i.e. in which node of the UTRAN the radio interface protocols are terminated, or equivalently, where within UTRAN the respective protocol services are accessible.
3rd Generation Partnership Project (3GPP): Technical Specification Group Radio Access Network, Physical Layer Procedures, 3G TS 25.322 v3.5.0, France, December 2000, specifies the RLC protocol. The RLC layer provides three services to the higher layers:                transparent data transfer service,        unacknowledged data transfer service, and        acknowledged data transfer service.        
In subsection 4.2.1.3 an acknowledged mode entity, AM-entity, is described (see FIG. 4.4 of the 3GPP Technical Specification). In acknowledged mode automatic repeat request, ARQ, is used. The RLC sub-layer provides ARQ functionality closely coupled with the radio transmission technique used. The 3GPP technical specification also reveals various triggers for a status report to be transmitted. The receiver shall always send a status report, if it receives a polling request. There are also three status report triggers, which can be configured                1. Missing PU(s) Detected,        2. Timer Initiated Status Report, and        3. Estimated PDU Counter.        
For trigger 1, the receiver shall trigger transmission of a status report to the sender if a payload unit, PU, is detected to be missing. (One PU is included in one RLC PDU.) With trigger 2, a receiver triggers transmission of a status report periodically according to a timer. Finally, trigger 3 relates in short to a timer corresponding to an estimated number of received PUs before the requested PUs are received. The 3GPP Technical Specification specifies a status PDU used to report the status between two RLC AM (‘Acknowledged Mode’) entities.
3rd Generation Partnership Project (3GPP): Technical Specification Group Radio Access Network, High Speed Downlink Packet Access (HSDPA), Overall Description, 3G TS 25.308 v5.3.0, France, December 2002, describes the overall support of High Speed Downlink Packet Access in UTRA. FIGS. 5.1-1 and 5.1-2 illustrate protocol architecture of HS-DSCH. Chapter 6 specifies HS-DSCH MAC architecture for the downlink.
3rd Generation Partnership Project (3GPP): Technical Specification Group Radio Access Network, UTRAN Overall Description, 3G TS 25.401 v4.5.0, France, September 2002, describes the overall architecture of UTRAN, including internal interfaces and assumptions on radio and Iu interfaces. Section 11.2.5 presents the DSCH Transport channel. DSCH scheduling is performed by MAC-c/sh in the CRNC.
3rd Generation Partnership Project (3GPP): Technical Specification Group Radio Access Network, Physical layer aspects of UTRA High Speed Downlink Packet Access, 3G TS 25.848 v4.0.0, France, March 2001, describes, among other things, physical layer aspect of the techniques behind the concept of high-speed downlink packet access (HSDPA). Section 6.3.1 presents a complexity analysis of a dual channel stop-and-wait protocol for downlink hybrid ARQ.
3rd Generation Partnership Project (3GPP): Technical Specification Group Radio Access Network, Physical layer aspects of UTRA High Speed Downlink Packet Access, 3G TS 25.950 v4.0.0, France, March 2001, describes several techniques for facilitating high-speed downlink packet access. Chapter 8 describes various properties of stop-and-wait hybrid ARQ.
None of the cited documents above discloses a method and system of reducing uplink retransmission delay of a radio communications system by introducing an uplink MAC ARQ layer of Node B. Further, none of the cited documents mentions a MAC PDU data indicator for soft combining control in Node B.